That means there is no confirmation ballots are being cast as voters intended or counted properly, the report says.

"To improve its overall election security, Delaware should stop using paperless [direct-recording electronic] machines that leave the state vulnerable to cyber attacks and prevents it from carrying out meaningful post-election audits to confirm the accuracy of election results," the report states.

First deployed in 1996, Delaware's 1,600 voting machines are among the oldest in the nation and have outlived their expected lifespan, creating a growing list of potential problems.

A state task force is currently reviewing proposals for new voting machines that will provide some kind of paper record, said State Elections Commissioner Elaine Manlove.

But the new equipment will not be in place until the 2020 election, at the earliest.

"If you gave me a check this afternoon, we could not buy those machines for 2018," Manlove told state legislators on Monday. "It's going to take time for us to make a decision and for them to be manufactured."

The lack of a paper ballot that can be double checked by voters before they submit their vote is not the only issue raised by the Center for American Progress.

The group also took issue with the fact that state law does not require precincts to reconcile the number of ballots cast at a polling site with the number of voters who signed in. Post-election audits also are not required by state law.

Manlove said reconciliation counts do occur, although the results are not published on the election department's website. The department, she said, also confirms results by hand counting absentee ballots if there is a discrepancy of 0.5 percent or more.

The Delaware Coalition for Open Government previously has raised concerns about the lack of post-election audits that would compare a random sample of ballots to the electronic record inside a voting machine.

The center's report also criticizes Delaware for allowing some disabled voters and those overseas to return ballots electronically, a practice the group says is "notoriously insecure."

Manlove said those ballots are submitted as a pdf, making them difficult to alter. She also noted that the system has received high marks from the Federal Voting Assistance Program.

"We've never had a problem and frankly, I think we're doing a fantastic job with that," she said.

Delaware's voting system earned a "D" grade from the center – one of 11 states to earn the same mark, including Pennsylvania and New Jersey. Five states received failing grades while 10 – including Maryland – earned a "B."

No states were awarded an "A."

The report comes less than six months after the U.S. Department of Homeland Security told Delaware and 20 other states that their election systems were targeted by hackers. Manlove has said the hackers attempted to gain access to Delaware's voter registration rolls but were unsuccessful.

The state election department also recently came under scrutiny by the nonpartisan voter advocacy group Campaign Legal Center. That group found Delaware's voter registration forms included outdated information that might have disenfranchised thousands of ex-felons whose voting rights were restored by state laws passed in 2013 and 2016.

A poll by the University of Delaware in advance of the 2016 presidential election found that 66 percent of state residents were concerned about voter fraud, 61 percent were worried about the election "being rigged" and 75 percent were worried about hackers breaking into the computers of state election systems.

The state's top election official said she hopes most concerns will be addressed after the state purchases new voting machines.

"There are a number of changes we are looking at," Manlove said. "But it all has to fall in place once we know what we'll be working with."